Ground return for plasma processes

Abstract

A method and apparatus for providing an electrically symmetrical ground or return path for electrical current between two electrodes is described. The apparatus includes at least on radio frequency (RF) device coupled to one of the electrodes and between a sidewall and/or a bottom of a processing chamber. The method includes moving one electrode relative to another and realizing a ground return path based on the position of the displaced electrode using one or both of a RF device coupled to a sidewall and the electrode, a RF device coupled to a bottom of the chamber and the electrode, or a combination thereof.

What is claimed is: 
     
         1 . A radio frequency return device for a plasma processing chamber, comprising:
 a base;   a first spring form coupled to the base and a second spring form coupled to an opposing side of the base, both of the first spring form and the second spring form comprising a first material made of a metal or metal alloy having an elastic property that is substantially the same at an ambient temperature and a processing temperature of about 200° C. or greater;   a second material substantially encasing the first material, the second material being different than the first material; and   a contact pad coupled to ends of the first spring form and the second spring form.   
     
     
         2 . The device of  claim 1 , wherein the second material is conductive and the first material is coated, wrapped or clad with the second material. 
     
     
         3 . The device of  claim 1 , wherein the first material retains about 85% of the elastic property at the processing temperature. 
     
     
         4 . The device of  claim 2 , wherein the second material includes a first property at the ambient temperature and a second property at the processing temperature, the first property and the second property being substantially different. 
     
     
         5 . The device of  claim 2 , wherein the coating, wrapping or cladding comprises an aluminum material. 
     
     
         6 . The device of  claim 5 , wherein the aluminum material comprises a foil material. 
     
     
         7 . The device of  claim 1 , wherein the elastic property is ultimate tensile strength. 
     
     
         8 . The device of  claim 1 , wherein the first material comprises a nickel-molybdenum-chromium alloy. 
     
     
         9 . The device of  claim 8 , wherein the second material comprises an aluminum material. 
     
     
         10 . The device of  claim 1 , wherein the shaft is coupled to a compression spring disposed in the base. 
     
     
         11 . A plasma processing system, comprising:
 a chamber; and   a first electrode disposed within the chamber, the first electrode facilitating generation of a plasma within the chamber and movable relative to a second electrode within the chamber, the first electrode being maintained electrically coupled while moving relative to the second electrode by a plurality of flexible contact members, at least a portion of the plurality of flexible contact members comprising:
 a base coupled to the first electrode; 
 a first spring form and a second spring form that comprise a metal or metal alloy that substantially retains elastic properties without plastically deforming when the material reaches a temperature above about 200° C. as compared to an elasticity at room temperature, the first spring form coupled to one side of the base and the second spring form coupled to a second side of the base opposing the first side. 
   
     
     
         12 . The system of  claim 11 , wherein the material is coated, wrapped or clad with a conductive material. 
     
     
         13 . The system of  claim 11 , wherein the portion of the plurality of flexible contact members further comprise:
 a base coupled to the first electrode; and   a shaft movably disposed in the base, wherein each of the portion of the plurality of flexible contact members coupled to the base at a first end and to the shaft at a second end.   
     
     
         14 . The system of  claim 13 , wherein the base comprises one or more bearing elements between the shaft and an opening formed in the base. 
     
     
         15 . The system of  claim 13 , wherein the shaft is coupled to a compression spring disposed in the base. 
     
     
         16 . The system of  claim 11 , wherein the at least one flexible contact member further comprises:
 a spring comprising a first material made of a metal or metal alloy having a having a mechanical property that is substantially the same at an ambient temperature and a processing temperature of about 200° C. or greater.   
     
     
         17 . The system of  claim 16 , wherein the first material is coated, wrapped or clad with a second material that is different than the first material. 
     
     
         18 . The system of  claim 17 , wherein the second material includes a first property at the ambient temperature and a second property at the processing temperature, the first property and the second property being substantially different. 
     
     
         19 . The system of  claim 11 , further comprising a shadow frame, wherein the shadow frame is grounded when in contact with the first electrode. 
     
     
         20 . A plasma processing system, comprising:
 a chamber;   a shadow frame disposed in the chamber; and   a first electrode disposed within the chamber, the first electrode facilitating generation of a plasma within the chamber and movable relative to a second electrode within the chamber, wherein the shadow frame is grounded when in contact with the first electrode and the first electrode is electrically coupled to the chamber while moving relative to the second electrode by a plurality of flexible contact members, at least a portion of the plurality of flexible contact members comprising:
 a base coupled to the first electrode; 
 a first spring form and a second spring form that comprise a metal or metal alloy that substantially retains elastic properties without plastically deforming when the material reaches a temperature above about 200° C. as compared to an elasticity at room temperature, the first spring form coupled to one side of the base and the second spring form coupled to a second side of the base opposing the first side.